This view of northeast Australia taken by the Aqua satellite vividly shows the many offshore reefs that together form the Great Barrier Reef. The Reef stretches more than 2,000 km (1,240 mi) along the coast of Queensland and is a UNESCO World Heritage Site. Between the reefs and the coastline bands of brown-green "streamers" may be discerned. These are blue-green bacteria (cyanobacteria) that form long overlapping strands and films that can cover immense areas becoming visible even from space. Sailors have long called these brown streamers "sea sawdust." Image courtesy of NASA.

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